1. Field of the Invention
The invention relates to a coaxial two-component cartridge.
2. Prior Art
Such coaxial two-component cartridges are advantageously manufactured so that the outer tube and the inner tube are manufactured separately. The two tubes must then be assembled together at a later time in order to obtain a coaxial cartridge. A suitable engagement must guarantee that the inner tube is rigidly anchored to the outer tube. The inner tube must not loosen when the cartridge is being transported or emptied. An inner tube that is not well-fastened, especially one that is no longer arranged in the center, can cause problems in an automatic emptying device because the emptying device might no longer be able to find the inner tube. Furthermore, when the cartridge is squeezed, the resulting internal pressure in the cartridge also acts on the floor of the inner tube, which can have the effect, if there is inadequate anchoring, of making the inner tube come loose, so that the cartridge can no longer be squeezed.
According to Utility Model DE 298 07 938 U1, two-part coaxial cartridges made from plastic are known. The engagement is released by a shoulder lying in one plane in the neck region of the outer tube and associated catch tabs on the inner tube. [Formation of] the shoulder in the outer tube is solved in terms of tool technology in that a separating plane is provided in the region of the shoulder. When opening the mold, here, the tool part engaging the tube above the separating plane is removed upward and the tool part engaging the tube below the separating plane is removed downward. With this method, it is possible to produce a shoulder with an arbitrary width, so that the locking tab can be engaged and held without a problem. However, because both sides must be removed from the mold, it is not possible with this design to produce a cartridge with a molded seal that is integrated with the outer tube. Instead, it requires an additional sealing cap, which means increased production and assembly costs.
In principle, the shoulder can also be demolded from the rear as an undercut, so that the cartridge can be produced in a closed configuration with a molded sealing cover. Because the undercut requires forcible ejection, the shoulder cannot be made with sharp edges and the width of the shoulder is limited to a few tenths of a millimeter. This leads to a greatly reduced, potentially inadequate, retaining force.
A two-part coaxial cartridge is known From DE 199 43 877 A1 in which the inner tube is produced from aluminum. Sawtooth-shaped ribs are formed on the inner tube. The aluminum ribs dig into the soft outer tube consisting of plastic during pressing and thus form a tight anchoring effect. The disadvantage of this solution is that the use of aluminum tubes is expensive, and a cartridge consisting of metal and plastic creates a problem ecologically with regard to disposal.